A high-diffusion-coefficient and high-brightness source is a light source required for many optical devices and optical measurement, for example, in the measurement of a high optical density, an ultrahigh diffusion coefficient and high brightness are required; otherwise, measured data cannot be unified. Commonly, light sources with the diffusion coefficient of over 0.9 and the brightness of over 1*104 cd/m2 belong to the high-diffusion-coefficient and high-brightness light source in the art. However, the higher the brightness is, the more difficult the high diffusion coefficient is to achieve, for example, the diffusion coefficient of the scheme of single opal glass designed by the National Institute of Standards and Technology (NIST) is only 0.91 and is difficult to completely meet regulations of the international standards ISO 5-2; and the scheme of opal glass and integrating sphere designed by the Physikalisch-Technische Bundesanstalt (PTB) can meet the regulations, but suffers from high luminous flux attenuation, i.e. the brightness is not high, and thus the measurement range is limited.